1. Field of the Invention
This invention relates to a portable gas chromatograph mass spectrometer particularly suited for chemical analyses in the field.
2. Description of Related Art
For safety reasons, it is often critical to quickly determine, to a high degree of accuracy, the level and type of contamination from unknown chemicals in certain environmental, industrial, civilian, or military settings. Although there are numerous methods of quantitative analysis, the instrumentation is typically cumbersome and not routinely field-deployable for on-site sample analysis. In particular, a gas chromatograph mass spectrometer (GC/MS) is a powerful tool that is routinely used in most analytical labs worldwide for the characterization and quantitative determination of known and unknown chemical species. A GC/MS carries out a mass spectrometric analysis for each constituent of the sample separated by the GC column, providing highly sensitive and accurate identification of each constituent.
However, most commercial GC/MS systems are non-portable, laboratory-based systems, or are only transportable when the necessary external support equipment (gas supply, vacuum system, computer, etc.) is also transported. In addition, most of the commercial systems are for analysis of volatile samples. Examples of GC/MS systems can be found in U.S. Pat. Nos. 5,686,655, 5,837,883, 5,313,061, and 5,083,450. The ""655 patent to Itoi shows a system in which the GC unit and the MS unit are mounted such that the system occupies less table-top or floor space. The ""061 patent describes a GC/MS system that has an internal volume of less than a cubic yard.
A need exists for a relatively lightweight, portable instrument that is a cost-effective and efficient means for analyzing on-site unknown chemical samples in a variety of emergency and non-emergency circumstances. To this end, a portable GC/MS system was designed and developed at Lawrence Livermore National Laboratory and is described in U.S. Pat. No. 5,525,799 to Andresen et al., which is hereby incorporated by reference. This system has been further improved to provide a portable, lighter, more compact, field reliable/serviceable GC/MS system for rapid on-site analysis of chemical unknowns.
The present invention is an improved portable gas chromatograph mass spectrometer (GC/MS). The object of this invention is to provide a relatively light-weight (approximately 55 lbs. or 25 kg) GC/MS unit, including the vacuum pumping system, that can perform qualitative and quantitative analyses of all sample types, including volatiles, liquids, and complex samples such as semi-volatiles, sludges, charred organics, and hazardous organics. The hand portable GC/MS system integrates a gas chromatograph, a mass spectrometer with a mass selective detector, several vacuum pumps, and an electronic control system with dedicated software. The entire GC/MS system is conveniently housed and configured in one enclosure, where the various components are modular and accessible for maintenance and serviceability.
A variety of hardware features have been incorporated into this portable GC/MS system, including a fail safe electronic system for automatic shutdown of the MS in the event of vacuum loss or run-away heaters; self-contained carrier gas supply for extending sample analyses, handling larger capillary GC columns, and prolonging the purge times; an auxiliary carrier gas line in the manifold system for optional hook-up to an external gas source; pump-out capability of the carrier gas line to conserve the use of carrier gas for sample analyses; and a GC injector with a small sample reservoir to enhance chromatography and compound detection limits. There is computer control for power time sharing between the heaters and the vacuum pump(s), resulting in lower peak power requirements.
One embodiment of the invention includes a xe2x80x9cstand-by modexe2x80x9d capability, in which vacuum pumps and heaters maintain the MS at operating or near-operating pressure and temperature conditions during transport of the GC/MS unit to the site of sample analyses. This innovative feature permits the GC/MS system to be transported under operating or near-operating conditions so as to eliminate or reduce the downtime (or ramp-up time) before samples can be analyzed on-site. The unit""s low power consumption enables the GC/MS to operate from a vehicle""s cigarette lighter jack via an inverter.
This portable GC/MS can be applied in many fields, including forensics and law enforcement, chemical weapons monitoring, hazardous materials monitoring and clean-up, environmental protection, military (i.e., high explosive and propellant analysis), food and drug analyses, international treaty verification work, and scientific field research. This GC/MS technology will be used by industry and the U.S. Government for field analyses and identification of known and unknown chemicals.
The foregoing and other objects, features, and advantages of the invention will become apparent from the following more particular description and as illustrated in the accompanying drawings.